A conventional valve mechanism having a pair of ceramic plate valves which are installed in a valve chamber of a mixing bibcock is shown in FIGS. 1 and 6 of Japanese Patent Publication No. 37179/1981, and in FIGS. 7 and 8 of the present application.
The valve mechanism shown in FIGS. 7 and 8 will now be briefly described.
A movable plate valve 40 has a mixing chamber 41 shaped as a downward-facing blind hole. The movable plate valve 40 is placed on top of a fixed plate valve 42. A hot water inlet port 43 and a cold water inlet port 44 in plate valve 42 are adapted to be freely opened and closed, and are adapted to be connected to an outlet 45 through the mixing chamber 41. The plate valve 40 is positioned in its forwardmost position and hot water inlet port 43 and the cold water inlet port 44 are closed when a lever 46 is positioned as shown by the solid lines. Hot water and cold water are discharged in equal quantities when the plate valve 40 is moved rearwardly when the lever 46 is pushed down to the horizontal position shown by the alternate long and two short dashed lines. More hot water is discharged when the lever 46 is turned horizontally to the right. The water is stopped when the lever 46 is restored to the central position and is tilted up. The movable plate valve 40, which is connected to the lever 46 by the valve shaft 47, moves backward and forward along a guide portion 49 connected to a guide groove 48 that is provided in the fixed plate valve 42 for the purpose of discharging or stopping the hot and cold water.
However, this structure has a problem in that the valve mechanism is not easy for children or people with handicapped hands to operate, and errors in operation tend to occur because the discharge and stopping of the hot and cold water is carried out by moving the lever vertically, and the discharge of hot and cold water, either separately or together, is carried out by moving the lever horizontally.
Furthermore, when the hot water inlet port is fully open, the water flow rate rapidly decreases. As a result, the temperature of the hot water must be adjusted whenever the hot water inlet port is fully open.
The mechanism of the connection between the fixed plate valve and the valve shaft is excessively complicated, because the movable plate valve is adapted to both turn and reciprocate. As a result, the number of parts is increased, and assembly and disassembly when a problem occurs is complicated, which adversely affects maintenance and productivity.